MicroRNAs, a class of 21-22 nucleotide non-coding small RNAs, are important regulators of gene expression and have been shown to modulate a broad range of cellular and developmental events. We have found that the expression of miR147 is upregulated in LPS stimulated cells and miR147 has anti-inflammatory properties which diminish activation in macrophages. Our data therefore suggest that specific microRNAs participate in regulating acute TLR4 induced inflammatory events and that modulation of microRNAs may have potential therapeutic benefit in life-threatening inflammatory conditions, such as ALI. Our hypothesis is that miR147 participates in the regulation of acute inflammatory responses and play a major role in determining the development, perpetuation, and severity of ALI. Our specific aims are: 1) To characterize the role of miR147 in regulating TLR4 induced inflammatory responses by delineating the mechanisms leading to LPS induced upregulation in the expression of miR147, elucidating the role that miR147 occupies in modulating LPS induced cellular activation, and delineating the mechanisms through which miR147 affects LPS induced cellular activation. 2) To explore if modulation of the expression of miR147 attenuates LPS induced ALI by determining the expression of miR147 in the lungs of LPS treated mice and exploring if modulation of miR147 expression can attenuate LPS induced ALI. The proposed studies should not only improve understanding of cellular mechanisms leading to ALI, but also are likely to suggest novel therapeutic interventions aimed at decreasing the incidence and/or severity of ALI. PUBLIC HEALTH RELEVANCE: MicroRNAs are important regulators of many essential cellular and developmental events. Deregulations of microRNA expression have been shown to be involved in a number of diseases, such as cancer, cardiovascular diseases, and diabetes. However, whether microRNAs regulate acute inflammatory responses and acute inflammation related diseases, including acute lung injury (ALI) has not been elucidated. We found that the expression of miR147 is upregulated in LPS stimulated macrophages and mouse lungs and miR147 has anti-inflammatory activities. The studies proposed in this application should not only improve understanding of the roles of microRNAs in regulation of LPS induced inflammatory responses and acute lung injury, but also are likely to suggest novel therapeutic interventions aimed at decreasing the incidence and/or severity of acute lung injury.